In recent years various types of plural component materials, particularly in the paints and coating areas, have become increasingly popular for a number of reasons. Such coatings offer a number of desirable properties such as durability and decreased environmental emissions. Such materials do present a problem, however, in that they need to be mixed only very shortly before they are applied to a product to be finished. Also, many are also quite sensitive in terms of the ratio between the two (or more) components involved.
While double sided pumps have been used in the past to pump plural component materials, that experience has been less than satisfactory for a number of reasons. For instance, U.S. Pat. No. 5,094,596 discloses utilizing a pump to pump different materials from the two sides but gives only an indication that a static mixer could be used, clearly unsatisfactory for continuous line processes where accurate ratio is at all times required. In addition, the pump mentioned in that patent is a relatively high pressure pump and is substantially more expensive than other types of pumps for many applications.
In addition, air-operated double diaphragm pumps have been utilized for a number of years in a split manifold configuration typically to pump windshield washer concentrate through one side and water through the other. There has been no criticality in such applications as it is not a continuous line process. Rather, the two components are merely batch mixed in the windshield washer reservoir or other container being filled and the complete batch ratio is all that is important.